The invention relates to air filters, including for internal combustion engines, and more particularly to an air filter with a failsafe filtered pressure tap.
Air filters are known in the prior art, and typically include a cylindrical housing having distally opposite axial ends, and a cylindrical main filter element in the housing, the main filter element having an annular sidewall with a hollow interior and extending between distally opposite axial ends. Air flows radially inwardly through the annular sidewall of the filter element into the hollow interior and then axially through the hollow interior and exits the housing. An outlet tube extends from the air outlet of the housing and conducts air therefrom. The outlet tube has a sidewall with a pressure tap opening therethrough communicating between the interior and exterior of the outlet tube, for sensing pressure in the outlet tube. A fitting is provided in the pressure tap opening for receiving a pressure sensor connector. The fitting typically includes an auxiliary filter element affixed thereto to prevent contamination of the interior of the outlet tube and the clean side of the main filter element.
In continuing development efforts directed toward weight and/or cost reduction, metal components are increasingly being replaced by plastic components, including housings and/or outlet tubes. In the case of a plastic outlet tube, a problem exists creating possible exposure of the interior of the outlet tube and the clean side of the main filter element to contamination from the pressure tap opening. The noted fitting in the pressure tap opening is typically metal and typically is internally threaded for receiving a pressure sensor connector. When not in use, the connector is removed, and the pressure tap opening is closed by a plug or bolt threaded into the fitting. The metal fitting is typically externally knurled, and is pressfit or sonically welded to the plastic outlet tube. When the pressure sensor connector or the plug is tightened into the metal fitting, it is possible to overtorque the latter and twist it out of or at least loosen it from the opening in the plastic outlet tube, due to the lower tensile strength of the plastic. In this manner, the metal fitting can fall out or otherwise become detached from the plastic outlet tube, which in turn creates a contaminating bypass through the pressure tap opening into the interior of the plastic outlet tube and the clean side of the main filter element.
The present invention addresses and solves the above noted problem and eliminates the possible contaminating bypass through the pressure tap opening to the interior of the plastic outlet tube and the clean side of the main filter element. Instead of affixing the auxiliary filter element to the metal fitting or otherwise making the auxiliary filter element part of the fitting, the auxiliary filter element is instead affixed to the plastic outlet tube in the pressure tap opening. The auxiliary filter element remains in the pressure tap opening if the metal fitting becomes dislodged from the plastic outlet tube and falls out of the pressure tap opening, such that the auxiliary filter element continues to protect the clean side of the main filter element and eliminates a possible contaminating bypass thereto through the pressure tap opening.